The FDA cried fraud in October, accusing companies in Florida, Colorado and California of illegally selling marijuana-derived products that supposedly could prevent, treat or cure cancer.

The advertising claims were unsubstantiated, said the FDA, and the products hadn’t been submitted for approval.

It was a public shaming that also served as a timely buyer-beware message for California, where the sale of marijuana will be expanded from medical purposes to recreational use in January.

With the prospect of big sales just ahead, the cannabis industry has been stressing that marijuana can be highly beneficial not only in health, but wellness.

Some of the claims are true, notably those involving marijuana’s value in treating pain. Physicians began pointing to that benefit long before California voters approved medical marijuana in 1996.

But consumers also are being exposed to ads and testimonials that conflict with the findings of the National Academy of Sciences, Engineering and Medicine, which struck a cautionary tone in January in a landmark report on the health effects of marijuana.

Scientists reviewed 10,000 cannabis studies and concluded that marijuana shows promise for such things as treating multiple sclerosis. But they also found lots to worry about, especially in the way marijuana affects the brains of adolescents. And the report says there’s not enough good data to determine whether marijuana can play a positive role in a wide variety of diseases and disorders.

The 468-page report claims that government hasn’t adequately supported cannabis research. It also says government is impeding progress by continuing to list marijuana as a Schedule 1 drug, which means that it has “no currently accepted medical use and a high potential for abuse.” Heroin is on the same list.

Scientists further say the government has devoted disproportionate attention to the potential harms of marijuana, ignoring possible benefits.

“I don’t want to give the impression that we don’t know anything; we do,” said Daniel Piomelli, a UC Irvine neurobiologist who served on the study team. “But we have a long way to go in assessing cannabis.”

The Union-Tribune examined the NAS report’s findings, many which are summarized here for the benefit of consumers and patients. The story also is based on interviews with scientists.

CANCER

The report reviewed a handful of the more than 100 types of cancer known to exist. Special attention was paid to such long-standing questions as: Does cannabis cause lung cancer?

The “evidence suggests” the answer is no, says the report, which is filled with the nuanced, qualified language common to science.

The report also says there is little or no evidence to determine if cannabis increases a person’s risk of other cancers, including esophageal, prostate, cervical, penile, anal and bladder cancer, as well as malignant gliomas, non-hodgkin lymphoma and Kaposi’s sarcoma.

“There is minimal evidence,” the report says, “that parental cannabis use during pregnancy is associated with greater cancer risk in offspring.”

On the upside: Cannabis can be effective in treating the nausea and vomiting that arises from chemotherapy.

HEART DISEASE, STROKE, DIABETES

Heart disease — which kills about 610,000 people a year in the U.S. — is fraught with uncertainty.

“The evidence is unclear as to whether, and how, cannabis use is associated with heart attack, stroke, and diabetes,” the report says.

The overview does specify that smoking cannabis regularly is linked to chronic coughing and phlegm production.” But people want to know more.

“I get a lot of questions about this from patients,” said Dr. Eric Adler, director of cardiac transplants at UC San Diego Health. “I tell them I think of cannabis smoke as being like tobacco smoke — it contains irritants. It could place you at risk for asthma and bronchitis.”

The cannabis industry has promoted the use of vaporizers as an alternative.

But those devices might not be much better, said Adler, noting, “The vapor still contains chemicals that might not be good for you. We don’t have long-term evidence yet to know what’s true.”

PAIN MANAGEMENT

“There is substantial evidence that cannabis is an effective treatment for chronic pain in adults,” the report says, a statement long made by physicians.

“One of the first things I ask new patients is, ‘Have you tried medical cannabis?’ “ said Dr. Mark Wallace, chair of the Division of Pain Medicine at UC San Diego Health.

“Many tell me they tried it but hated it. I ask them if they got any guidance on proper dosage, and most say no. That’s where you usually find the problem.

“If they get the right, low dosage, they usually do OK. The cannabinoids and THC in marijuana have anti-inflammatory properties.”

Wallace says he has used marijuana to successfully treat neuropathic pain, which can be caused by such things as diabetes, traumatic injuries and certain types of infections. His patients also have used cannabis to treat arthritis and fibromyalgia, which haven’t been extensively studied in clinical trials.

“Fibromyalgia was one of those syndromes where we used to throw up our arms because there wasn’t a good treatment,” Wallace said. “People would be given opioids, or worse. I’ve been getting good results with medical cannabis, including helping people to get off opioids.”

PSYCHOSOCIAL

The report affirms the long established belief that marijuana can affect a person’s ability to think, remember, learn and pay attention. The reviewers cited particular concern about adolescents, saying cannabis can affect academic achievement and slow the development of social skills.

There is positive news from a different source.

The National Institute of Drug Abuse said in its 2016 Monitoring the Future report that there has been a “continued long-term decline in the use of many illicit substances, including marijuana, as well as alcohol, tobacco, and misuse of some prescription medications, among the nation’s teens.”

MENTAL HEALTH

The report says, “Cannabis use does not appear to increase the likelihood of developing depression, anxiety, and post-traumatic stress disorder.” But “heavy users are more likely to report thoughts of suicide than non-users.”

And it what may seem like a contradiction, the reviewers say that cannabis use might increase the risk for schizophrenia and other psychoses, But people with these disorders might perform better on learning and memory tasks if they have a history of marijuana use.

IMMUNE SYSTEM

The report says scientists haven’t figured out whether cannabis is good or bad for the human immune system, including whether marijuana could hurt the immunity of people with HIV.